Conventionally, when biopsies were desired to be taken of the lymph nodes, for example, so as to aid in the diagnosis of carcinoma, the prior techniques would all typically utilize a substantially rigid needle and penetrate the body via percutaneous entry. For example, U.S. Pat. Nos. 3,630,192 and 3,628,524 each to Jamshidi disclose biopsy needles suitable for percutaneous entry. More recently, less invasive flexible biopsy instruments which do not require percutaneous entry have been described. U.S. Pat. No. 4,249,541 to Pratt discloses that a flexible biopsy instrument can be utilized in combination with a fiberoptic bronchoscope.
U.S. Pat. No. 4,617,940 to Wang, the entirety of which is incorporated herein by reference, describes a completely flexible bronchoscopic needle assembly wherein relatively non-invasive biopsy procedures can be performed utilizing a needle in combination with a fiberoptic bronchoscope. The attending physician inserts the bronchoscope into a predetermined one of the patient's natural orifices, or other site, depending upon the particular portion of the body one desires to obtain a sample of tissue to be biopsied. The needle assembly, which includes an outer catheter and an inner coaxial stylet attached to a retractable needle, is slideably inserted into a receiving passageway of the bronchoscope. The needle, directly connected to the proximal end by a stiff wire, is urged into the tissue of the patient by a stabbing force exerted on the proximal end of the stylet (e.g. the end on the exterior of the patient's body) after the outer catheter comes into the bronchoscope's field of view. The bronchoscope enables the attending physician to accurately position the needle and to penetrate the exact location of the desired tissue area due to the viewing capabilities provided thereby.
A particular problem in utilizing a flexible bronchoscopic needle is that the needle assembly must be flexible enough to allow the physician to maneuver the assembly to the target site, but yet rigid enough to allow penetration of the needle into the target tissue. The bronchial wall or hard tumor tissue will frequently need to be penetrated and may present significant resistance to entry of the needle. Thus, upon arrival to the target site, the needle assembly, particularly the distal portion of the needle assembly, needs flexibility to directionally maneuver around bends and curves, yet also needs to be rigid enough to provide a countering pressure against the resistance provided by the bronchial wall or hard tumor tissue. Conventional flexible needle assemblies have not provided satisfactory means for balancing the necessary flexibility with the desired rigidity as the needle is directed toward the target tissue. Thus, a need exists for a needle assembly having flexible characteristics as the assembly is maneuvered through a scope or other device while also having rigid characteristics as the needle is inserted into the target tissue.